package com.yang.springcloud.lb;

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

@Component
public class MyLB implements LoadBalancer {

    // 用于统计当前的访问次数
    private AtomicInteger atomicInteger = new AtomicInteger(0);

    /**
     * @return 当前是第几次访问
     */
    public final int getAndIncrement(){
        int current, next;
        // 自旋锁
        do {
            current = this.atomicInteger.get();
            next = current >= 2147483647 ? 0 : current + 1;
        }while (!this.atomicInteger.compareAndSet(current, next));
        System.out.println("【 当前访问次数 】 next = :"+next);
        return next;
    }

    @Override
    public ServiceInstance instances(List<ServiceInstance> serviceInstances) {
        // 通过取余，计算出当前应该是哪一个 Provider 提供服务
        int index = getAndIncrement() % serviceInstances.size();
        ServiceInstance instance = serviceInstances.get(index);
        System.out.println("当前是 【" + instance.getUri() + "】 提供服务");
        return instance;
    }
}
